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MIT Grad student - High current at high frequency into low-resistance loads

Other Parts Discussed in Thread: OPA549

Hi,

I am an MIT grad student currently working on a research project in the lab. The project requires me to send very high sinusoidal current into a low resistance load at high frequencies. In terms of numbers, we would like to send 0.1V across 0.001-0.01Ohms, which means we need 10A-100A, all of that at 1-50MHz. Since our waveform generator have low power and 50Ohms output impedance, we can't use them directly to drive that.


I've been thinking of using high-current op amps like the OPA549 as unity gain buffers to help me achieve that. Would you recommend that method? If not, what devices and methods would you recommend to help me send that signal?


THanks,

Ruben

  • Hello Ruben,

    When considering the 1 to 50 MHz frequency range that your system will cover one finds that the OPA549 doesn't have enough bandwidth to cover it. Viewing the MAXIMUM OUTPUT VOLTAGE SWING vs FREQUENCY graph on data sheet page 6 shows that the useable bandwidth drops off quickly after about 50 kHz due to slew rate limiting. It just simply isn't the correct device for the application.

    One to 50 MHz spans radio frequencies across MF, HF and low VHF segments of the spectrum, which is actually a very wide range any one amplifier to cover. Therefore, you are looking for some sort of RF power amplifier solution that exceeds what operational amplifers can do. There may be some very fast power MOSFET solution that could provide the very high current over that frequency range, but our expertise on this E2E forum is not in that area.

    Regards, Thomas

    PA - Linear Applications Engineering

  • Hi Thomas,

    Thank you for your answer! I'll be sure to have a look at the equipment you suggested.

    Best regards,

    Ruben